1. Field of the Invention
This invention relates to an aerodynamic braking system for use in recovering a space vehicle, and for returning a space vehicle from space and placing it into a low earth orbit where it can be recovered and/or refurbished for reuse.
2. Description of the Prior Art
A principal object of the present invention is to provide a low cost system for rendering a space vehicle reusable. There is a need for such a system for use, for example, with space vehicles planned for traveling round trip between a low earth orbit (LEO) and a geosynchronous earth orbit (GEO) --a mission which will involve a change in velocity of approximately 28,670 feet per second during the round trip.
The kinetic energy of a spacecraft during reentry is many times greater than the amount of energy which in terms of heat, would be needed to bring about complete vaporization of the spacecraft. Retardation and friction with the air on reentry into the earth's atmosphere would release a considerable amount of heat and burn up the reentering body. Indeed, this is the normal fate of meteorites entering the atmosphere from outer space.
The "ablating reentry shield" is a known successful way of preventing space vehicle destruction during reentry. Made of ablative material, the shield dissipates heat by melting and vaporizing. Friction with the air heats the ablative material to a temperature of several thousand degrees centigrade, so that the material becomes liquid and "boils off". The zone immediately behind a shock wave which is formed ahead of the returning space vehicle is heated to about 6,000.degree. C. and is in the gaseous state. About 80% of the thermal energy from the intermediate layer between the liquid and the gaseous layer is dissipated as radiation to the surrounding air. The low conductivity of the still-solid ablative material prevents any substantial amount of heat from penetrating into the space vehicle itself during the reentry. (Which is only 200-300 seconds in duration.)
Ablative insulation is lightweight and is adequate for the heat load encountered during a reentry, but it requires that the vehicle be returned to the earth after each flight for a very expensive refurbishment.
Many proposals of using a fluid layer for protecting an aircraft and/or reentry vehicle surface against overheating may be found in the patent literature. Examples of such systems are disclosed by the following U.S. patents:
U.S. Pat. No. 1,426,907, granted Aug. 22, 1922, to George Ramsey; PA0 U.S. Pat. No. 2,468,820, granted May 3, 1949, to Robert H. Goddard; PA0 U.S. Pat. No. 2,995,317, granted Aug. 8, 1961, to Fritz Schoppe; PA0 U.S. Pat. No. 3,026,806, granted Mar. 27, 1962, to Leslie A. Runton and Henry C. Morton; PA0 U.S. Pat. No. 3,062,148, granted Nov. 6, 1962, to John P. Le Bel; PA0 U.S. Pat. No. 3,113,750, granted Dec. 10, 1963, to Melville W. Beardsley; PA0 U.S. Pat. No. 3,259,065, granted July 5, 1966, to Don H. Ross and Eugene S. Rubin; PA0 U.S. Pat. No. 3,298,637, granted Jan. 17, 1967, to Shao-Tang Lee; PA0 U.S. Pat. No. 3,508,724, granted April 28, 1970, to Stanley H. Scher and James C. Dunavant; PA0 U.S. Pat. No. 3,624,751, granted Nov. 30, 1971, to Ronald F. Dettling; PA0 U.S. Pat. No. 3,731,893, granted May 8, 1973, to Charles J. Stalmach, Jr.; PA0 U.S. Pat. No. 3,785,591, granted Jan. 15, 1974, to Charles J. Stalmach, Jr.; and PA0 U.S. Pat. No. 4,014,485, granted Mar. 29, 1977, to Laird D. Kinnaird and Seth B. Moorhead, Jr.
The above patents and the prior art that is discussed and/or cited therein should be studied for the purpose of putting the present invention into proper perspective relative to the prior art.